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• Mixing audio, given timestamps. How to do it efficiently ?

  2 août 2021, par Evil

  I have two stereo sounds, 1.wav and 2.wav, these sounds are less than 1 second long and list of timestamps (miliseconds from start of recording). Recording of pure video (recording.mp4) is several hours long and there are thousands (20 000 - 30 000) of timestamps per sounds.

  


  I want to convert list of timestamps and sounds into one recording, merging it with video. The part of merging audio with video is easy with ffmpeg, so this is not part of the question.

  


  The list of timestamps is tsv, for example :

  


  


  1201\t1.wav
  
1501\t2.wav
1603\t1.wav
  
and so on, up to 50 000

  


  


  I can convert it to anything, I am generating this file.

  


  I have seen mixing sound with padding and mixing audio to existing video, but I have to batch process a lots of samples, running sox that many times is not feasible. Mere onstructing input for ffmpeg or sox is a cumbersome task.

  


  I do not use any effects on sounds. There is no explicit support in sox to take one input and play it multiple times (echo / echos destroys the material). Also creating padding or delay takes a lot of time. FFMPEG also needs long query to make it happen.

  


  Since muxing two files is easy, I have tried to record two sounds separately, but still it takes a lot of time to process.

  


  Is there simpler / faster way ?

  


• Extracting audio features

  27 avril 2023, par Srinjoy Chatterjee

  I am working on extracting features from an audio file to build a recommendation system.

  


  So far I am able to extract tempo, beat-times, loudness and pitch class using librosa and ffmpeg.

  


  My question how we can extract/detect features as Danceability, Energy, Acousticness, Speechiness, Valence without using Spotify API. Are there any libraries or algorithm using which we can do so.

  


• image sequence to Video. Faster Way to Render "Hold" frames in FFMPEG (without duplicating image)

  11 septembre 2014, par dprogramz

  I’m working on a project that converts a Flash Movie with dynamic input to Apple Animation Codec.

  It’s to generate messaging, so there is some animation, then the message holds, then animation resumes, etc. The hold times are user variable.

  I’m first converting the SWF to PNGs by sending a bitstream via the actionscript3 PNGEncoder library, and using a PHP script to save the bitstream to the server as a series of temp png files. This is working very fast.

  from flash ill get an image sequence like this :

  frame000.png-frame014.png

  frame0200.png-frame250.png

  frame350.png-frame400.png

  frames 15-199 are all the same image holding. I’m not sending bitstreams for the holding images to save bandwidth and time, it would be redundant to send the same image file 185 times. Right now I am copying frame14.png with incrementing file numbers. I have to do this for each instance there is a hold frame.

  After all the hold frame holes are filled I then run FFMPEG on the complete image sequence to generate the video.

  Is there any faster way to do this ? The longer the hold (which is variable by the user) the longer it takes to render. I understand that there will be some extra render time, but it’s a repeated image and in other conversion programs does not take nearly as long. Or is my current way of doing it the only way in this instance ?

  When rendering out of a program like after effects, the animation codec seems to dynamically adjust the frame rate for hold frames.

  Thanks for the help and insight !!